What is the due date for business income tax returns?

Some business entities' income tax returns have due dates other than April 15. The instructions for each type of form note the appropriate due date:

Note: For any due date that falls on a Saturday, Sunday, or legal holiday, the due date is the next business day. The term “legal holiday” means any legal holiday in the District of Columbia. Refer to Publication 15 (Circular E), Employer’s Tax Guide, Section 11, Depositing Taxes – Deposits Due on Business Days Only.